/*
 * Copyright (C) 2004, 2005 Joe Walnes.
 * Copyright (C) 2006, 2007, 2009, 2013 XStream Committers.
 * All rights reserved.
 *
 * The software in this package is published under the terms of the BSD
 * style license a copy of which has been included with this distribution in
 * the LICENSE.txt file.
 * 
 * Created on 02. September 2004 by Joe Walnes
 */
package com.feilong.lib.xstream.io.path;

import java.util.ArrayList;
import java.util.List;

import com.feilong.lib.xstream.core.util.FastStack;

/**
 * Represents a path to a single node in the tree.
 *
 * <p>
 * Two absolute paths can also be compared to calculate the relative path between them.
 * A relative path can be applied to an absolute path to calculate another absolute path.
 * </p>
 * 
 * <p>
 * Note that the paths are normally XPath compliant, so can be read by other XPath engines.
 * However, {@link #toString()} will select a node list while {@link #explicit()} will always select
 * an individual node. If the return type of the XPath evaluation is a node, the result will be the same,
 * because XPath will then use the first element of the list. The following are examples of path
 * expressions that the Path object supports:
 * </p>
 *
 * <p>
 * Note that the implementation does not take care if the paths are XPath compliant, it simply
 * manages the values between the path separator. However, it normalizes the path if a path element
 * ends with a selector for the first element (i.e. "[1]"). Those will be handled transparent i.e. two Paths
 * are treated equal if one was created with path elements containing this selector and the other one
 * without.
 * </p>
 * 
 * <p>
 * The following are examples of path expressions that the Path object supports:
 * </p>
 * <ul>
 * <li>/</li>
 * <li>/some/node</li>
 * <li>/a/b/c/b/a</li>
 * <li>/a/b[1]/c[1]/b[1]/a[1]</li>
 * <li>/some[3]/node[2]/a</li>
 * <li>../../../another[3]/node</li>
 * </ul>
 *
 * <h3>Example</h3>
 *
 * <pre>
 * 
 * Path a = new Path("/html/body/div[1]/table[2]/tr[3]/td/div");
 * 
 * Path b = new Path("/html/body/div/table[2]/tr[6]/td/form");
 *
 * Path relativePath = a.relativeTo(b); // produces: "../../../tr[6]/td/form"
 * 
 * Path c = a.apply(relativePath); // same as Path b.
 * </pre>
 *
 * @see PathTracker
 *
 * @author Joe Walnes
 */
public class Path{

    private final String[]    chunks;

    private transient String  pathAsString;

    private transient String  pathExplicit;

    private static final Path DOT = new Path(new String[] { "." });

    public Path(String pathAsString){
        // String.split() too slow. StringTokenizer too crappy.
        List result = new ArrayList();
        int currentIndex = 0;
        int nextSeparator;
        this.pathAsString = pathAsString;
        while ((nextSeparator = pathAsString.indexOf('/', currentIndex)) != -1){
            // normalize explicit paths
            result.add(normalize(pathAsString, currentIndex, nextSeparator));
            currentIndex = nextSeparator + 1;
        }
        result.add(normalize(pathAsString, currentIndex, pathAsString.length()));
        String[] arr = new String[result.size()];
        result.toArray(arr);
        chunks = arr;
    }

    private String normalize(String s,int start,int end){
        if (end - start > 3 && s.charAt(end - 3) == '[' && s.charAt(end - 2) == '1' && s.charAt(end - 1) == ']'){
            this.pathAsString = null;
            return s.substring(start, end - 3);
        }else{
            return s.substring(start, end);
        }

    }

    public Path(String[] chunks){
        this.chunks = chunks;
    }

    @Override
    public String toString(){
        if (pathAsString == null){
            StringBuffer buffer = new StringBuffer();
            for (int i = 0; i < chunks.length; i++){
                if (i > 0){
                    buffer.append('/');
                }
                buffer.append(chunks[i]);
            }
            pathAsString = buffer.toString();
        }
        return pathAsString;
    }

    public String explicit(){
        if (pathExplicit == null){
            StringBuffer buffer = new StringBuffer();
            for (int i = 0; i < chunks.length; i++){
                if (i > 0){
                    buffer.append('/');
                }
                String chunk = chunks[i];
                buffer.append(chunk);
                int length = chunk.length();
                if (length > 0){
                    char c = chunk.charAt(length - 1);
                    if (c != ']' && c != '.'){
                        buffer.append("[1]");
                    }
                }
            }
            pathExplicit = buffer.toString();
        }
        return pathExplicit;
    }

    @Override
    public boolean equals(Object o){
        if (this == o){
            return true;
        }
        if (!(o instanceof Path)){
            return false;
        }

        final Path other = (Path) o;
        if (chunks.length != other.chunks.length){
            return false;
        }
        for (int i = 0; i < chunks.length; i++){
            if (!chunks[i].equals(other.chunks[i])){
                return false;
            }
        }

        return true;
    }

    @Override
    public int hashCode(){
        int result = 543645643;
        for (String chunk : chunks){
            result = 29 * result + chunk.hashCode();
        }
        return result;
    }

    public Path relativeTo(Path that){
        int depthOfPathDivergence = depthOfPathDivergence(chunks, that.chunks);
        String[] result = new String[chunks.length + that.chunks.length - 2 * depthOfPathDivergence];
        int count = 0;

        for (int i = depthOfPathDivergence; i < chunks.length; i++){
            result[count++] = "..";
        }
        for (int j = depthOfPathDivergence; j < that.chunks.length; j++){
            result[count++] = that.chunks[j];
        }

        if (count == 0){
            return DOT;
        }else{
            return new Path(result);
        }
    }

    private int depthOfPathDivergence(String[] path1,String[] path2){
        int minLength = Math.min(path1.length, path2.length);
        for (int i = 0; i < minLength; i++){
            if (!path1[i].equals(path2[i])){
                return i;
            }
        }
        return minLength;
    }

    public Path apply(Path relativePath){
        FastStack absoluteStack = new FastStack(16);

        for (String chunk : chunks){
            absoluteStack.push(chunk);
        }

        for (String relativeChunk : relativePath.chunks){
            if (relativeChunk.equals("..")){
                absoluteStack.pop();
            }else if (!relativeChunk.equals(".")){
                absoluteStack.push(relativeChunk);
            }
        }

        String[] result = new String[absoluteStack.size()];
        for (int i = 0; i < result.length; i++){
            result[i] = (String) absoluteStack.get(i);
        }

        return new Path(result);
    }

    public boolean isAncestor(Path child){
        if (child == null || child.chunks.length < chunks.length){
            return false;
        }
        for (int i = 0; i < chunks.length; i++){
            if (!chunks[i].equals(child.chunks[i])){
                return false;
            }
        }
        return true;
    }
}
